1. Technical Field
The present invention relates to a light guide plate used for a head-mount display or the like used while worn on the head, and a virtual image display device incorporating the light guide plate.
2. Related Art
In recent years, as a virtual image display device making it possible to form and observe a virtual image such as a head-mount display, there have been proposed various devices of a type of guiding the picture light from the display element to the pupils of the observer using a light guide plate. As such a light guide plate for a virtual image display device, there has been known a light guide plate, which guides the picture light using total reflection, reflects the picture light with a plurality of partial reflecting surfaces disposed in parallel to each other at a predetermined angle with a principal surface of the light guide plate, and thus outputs the picture light to thereby make the picture light reach the retinas of the observer (see JP-T-2003-536102 (Patent Document 1). In such a light guide plate, a part of the picture light passes through the plurality of partial reflecting surfaces a plurality of times, and is taken in the direction toward the eyes. Therefore, the brightness variation and the picture variation are apt to occur in the picture light due to the difference in the number of times of passage through the partial reflecting surfaces, and in order for preventing the variations, devices for relatively adjusting the reflectance and the relative distance between the two or more of the partial reflecting surfaces have been made (Patent Document 1). Further, as a similar technology, there has been known a device of providing a reflecting layer to the sawtooth portion in order for taking out the picture light (see JP-A-2004-157520 (Patent Document 2)).
However, in the case of, for example, Patent Documents 1 and 2 mentioned above, it is required to accurately adjust the reflectance and the relative distance between the partial reflecting surfaces in order for preventing the brightness variation and the picture variation in the image light as the picture light or the like. Further, in the case of Patent Documents 1 and 2, since there is adopted the structure of making the light pass through the members for performing reflection a plurality of times when taking out the image light from the light guide plate by the reflection, the light efficiency cannot help but be relatively low.